Method and means for fabricating printing plates



Oct. 10, 1939. A. H. MARQQT 2,175 439 METHOD AND HEARS FOR FABRICATING PRINTING PLATES Filed Aug. 6, 1937 2 Sheets-Sheet l w MW MW W 1 INVENTOR W H W X BY Patented Oct. 10, 1939 UNITED STATES PATENT OFFICE METHOD AND MEANS FOR FABRICATIN'G PRINTING PLATES 6 Claims.

This invention relates to the fabrication of plates used in the printing art, especially to the production of printing plates such as half-tone plates etched or engraved on zinc, copper or other suitable metals, and more particularly to the provision of bumper plates, by which the correct high lights, shadows and analogous effects are produced in the final product.

The conventional method of fabricating such plates most commonly in use at the present time is to make for the intended purpose a primary printing plate, and a separate auxiliary bumper plate, and then to fasten this auxiliary plate to the primary plate, the compound plate thus formed being used in the formation of a matrix for the final printing plate, with a corresponding and excessive expenditure of material, time and labor, and with a liability to error which always attends such additional operations.

Other undesirable operations incidental to practice of the conventional method, include those incidental to the use of asphaltum as a protective coating upon the plate during certain stages of the process, and the consequent need for cleansing the plates and removing the asphaltic residuum from various parts of the apparatus and from the solutions contaminated thereby, and also from the dragons blood etching powder, in which grains of asphaltic material are likely to persist, in spite of the greatest care, with resultant impairment in the delicacy of tone in the final print.

In the operation of sensitizing the plates, preparatory to their exposure and development, it is customary for the operator to hold the plate in one hand, and use the other hand to direct over the plate the flow of sensitizing liquid, usually in several waves, much of the solution running to waste.

Owing to the flow of solution over the hands of the operator, bichromate poisoning often supervenes, and the manual process of sensitizing is at its best a difficult and dangerous operation, resulting in constant staining of the hands.

Under such conditions, an object of the present invention is to provide a novel method and means for fabricating a printing plate of the above character in which, by a single preparatoryoperation, the printing plate is provided, on that face which is to function for printing, with a suitable coating of light-sensitive solution, and on its reverse face with a protective coating which is constituted by a layer of the same sensitizing solution, adapted to be converted into plate-protect- 55 ing condition simply by the usual steps of development and fixation subsequent to exposure, thus obviating completely the need for asphaltic protection at any time, and eliminating all of the disadvantages attendant thereupon, including those briefly mentioned above. 5

A cognate object-of the invention is to provide a bumper" plate integrally formed with the printing plate, by exposing the above-mentioned sensitized reverse side to the action of light through a positive or secondary negative element made either on a film or on cellulosic sheet material, such as paper, of suitable transparency or translucency, having first preformed this print from the master negative of the subject to be reproduced so that the negative imposes its image on the one side of the printing plate and the other side is printed through the secondary paper negative or positive obviating entirely any need forthe formation of an auxiliary bumper plate, together with the preparatory steps preliminary to such formation and its attendant expense, delays, errors and inconveniences.

Among other and ancilliary objects of the improved method herein disclosed is the provision for exposing both of the sensitized faces of the plate at the same time, and preferably for the same period of time, thus reducing to a minimum the time needed for production of the bumper feature.

The invention has for a further object of importance the provision of apparatus of improved character by which the above recited novel method of sensitizing the printing and bumper faces of a plate may be carried into effect rapidly, accurately and at a single submersion, and in such a way that subsequently to such submersion, the plate is provided not only with the printable image on one side, but also with the essential basis for a protective coating on the other side. This protective coating is matured over the entire inactive portion of thereverse side of the plate simply by the regular development and fixation of the sensitized surfaces, which may be carried out upon the plate as a whole. The result is a protective coating which prevents access of oxygen to the portions of the reverse side so protected, throughout the life of the plate, and without the need for a special coating of grease 1 or other protective medium. a 1

The provision of a plate-carrier of novel struc- 5o ture, especially useful in effecting the submersion of a plate, or simultaneously of a pair of plates, in the sensitizing apparatus, and associated with supporting means forming part of the co-ordinated apparatus, constitutes another of the objects 'of the invention, which includes also the provision of a device in the nature of a pair of tongs of novel construction adapted to grasp plates of different sizes at their edges, and to facilitate the manipulation of the plates at the different stages of their fabrication, including particularly the preparatory stage of rinsing and drainage of the plates preliminary to their introduction into the sensitizing apparatus.

Another object of the invention is to provide for such circulation of the sensitizing liquid that it is substantially self-clearing, in the respect that any foreign matter. such as particles of dust, fluff, and the like, will pass off from the atmospheric-liquid level, being entrained in a current flowing from each of the inlets toward each of the outlets, thus keeping away from the sensitizing body of liquid all floating matter likely to gather upon the plate when withdrawn.

In general, also, it is the object of the invention to reduce the expense of fabrication by using only a very thin coating of the sensitizing solution, and this thin coating I have found to constitute an ideal medium for the formation of a clear printing image and for like formation of a bumper image which will produce the intended complemental effect which insures'good definition in the final printing.

Other objects and features of the invention will be made to appear as the description of the particular physical embodiment selected to illustrate the invention progresses.

In the accompanying drawings, like characters of reference have been applied to corresponding parts throughout the several views which make up the drawings, in which:

Fig. l is a view in sectional elevation of an apparatus for sensitizing printing plates in the construction of which the present invention has been embodied; Fig. 2, is a view thereof in end elevation, looking from right to left; Fig. 3 is a view in vertical section, taken on the line IIIIII of Fig. 1; Fig. 4 is a fragmentary, detail view in longitudinal, vertical section, taken on the line IV-IV of Fig. 2, and also showing in dash-dot lines a different position of the printing plate and its supporting appliances; Fig. 5 is a view in horizontal section, taken on the line V-V of Fig. 4; Fig. 6 is a fragmentary detail view in vertical section, taken on a larger scale, of the plateholder shown in Fig. 4 with two plates in position for the sensitizing operation; Fig. 7 is a view in perspective of a pair of plate tongs adapted for use in the manipulation of the plates under treatment according to the method of the present invention.

In the now-preferred form of apparatus selected for illustration and description in order to permit ready and complete understanding of my novel method for the fabrication of plates of the class described, adapted to be used in the printing art, the part designated by the reference character H is a container for liquid, made of a suitable material, such as galvanized sheet metal, and of any suitable shape, being herein illustrated as of rectangular cross-section, considerably greater in breadth than in thickness and somewhat less in height than in breadth.

An inlet for liquid is shown at 12, in the lower left hand corner, and an outlet or overflow at l3 in the upper right hand corner, so that the liquid M can be maintained in known fashion at the level indicated, primarily for the purpose of modulating the temperature of the environment in which the method is carried out.

Within the container H is provided a similarly shaped compartment l5, which, in turn, encloses a receptacle l6, of like shape and of suitably smaller dimensions to permit its easy insertion and removal from the compartment l5, as oocasion may require.

By forming the receptacle 16 with only sufficient clearance for the movement of the plate and its supporting holder vertically, it is possible to use a relatively small body of sensitizing solution.

If desired, small projections as those indicated at 9, may be formed in the walls of the compartment, or of the container, or of the receptacle,

. to aid in spacing the adjacent wall apart proper- The compartment l5 has generally imperforate walls, except that it is provided, as at IT, on each end, with an overflow pipe, beneath which is a flask l8 supported by a bracket in and designed to recover for further use any sensitizing liquid S which may rise above the intended level in the plate receptacle l6, especially when a plate is inserted. Upon reference to Fig. 3. it will be apparent that the liquid level in receptacle IE will be maintained constant with that in compartment I5, for the reason that orifices l9 and 2!), suitable for that purpose, are provided in the adjacent walls. The flow of sensitizing material near the surface of the body thereof in the platereceptacle and container carries toward the outlets ll all of the loose matter lying on or near the surface.

In pursuance of the invention. a reserve supply of the sensitizing liquid, designated S, is maintained in an overhead tank 2| (Fig. 1) from which it is biased by gravity to descend, as needed, under the control of a valve-segment 23, formed upon a ball-lever 24, swinging upon a pivot 25 and adapted to open and to close an orifice 26 in the supply tank 2|. Further communication between the compartment I5 and the plate receptacle I8 is afforded by perforations 21 in the bottom wall 28 of the latter. Its side walls 29 are corrugated, preferably, as illustrated (see Fig. 5) both for the sake of providing added strength for a given thickness of sheet metal, and also to add somewhat to the intramural space 30, in which any sediment may be allowed to descend into the bottom space 3|, from which such ac cumulation can be removed easily upon removal of the receptacle 16 from the compartment l5, which operation is rendered easy by the provision of hook-like handles 32, one at each end of the receptacle. The latter is supported at the desired height above the bottom 33 of compartment I5 by feet 34 (Fig. 4), and similar feet 35 support the compartment l5 above the bottom wall 36 of the container ll. Other spacer devices may be provided wherever needed, as for example at the top of the apparatus. where lugs 31 are formed, one at each side of the assembly, being offset, in the instance illustrated, from the mid-portion of the upper edge of the side wall of the compartment IS.

The tankor container H may desirably be bolted as by braces B (Fig. 2), to a suitably solid foundation B", use being made of bolts B. A hinged cover 38 serves to close the tank H.

The compartment l5 has a drain in its bottom,

closed by a plug Him, and wherever desired, access to this plug for aiding to drain the receptacle may be had by first lifting the receptacle out of the compartment, then lifting the compartment out of the container, and then removing the plug I62, and draining the compartment,

which may also be flushed out through the opened drain.

By suitable attention of the above nature, the sensitizing solution is maintained in a satisfactory condition of thinness, insuring the formation of a good sensitized coat on both sides of the plate.

In pursuance of a further important object of the invention, provision is made by me of a plate-holder adapted to permit'the manipulation with unusual case of the metal plates which are to be sensitized in the solution S contained in the receptacle I, for which purpose the plates must be first submerged in the solution and then withdrawn therefrom; and as a preliminary to such submersion, the plates must be inserted into the plate holder with a minimum of handling, i.e., of contact with the hands of the operator.

For the above purpose, the invention provides a plate-holder comprising an upright member 4., having at its lower end a transverse ledge 01' foot 4| of suitable form, andwhich is preferably of the shape illustrated in Fig. 6 in cross-section, having when so viewed the aspect of the letter W. whereby it is adapted to serve for the support simultaneously of two plates, as shown, each of the plates, as P and P", resting at its lower edge in one of the V-shaped troughs of the ledge 4|. The holder so illustrated can be used with only one plate In order to insure a very solid support for the plates, inasmuch as a plate of say 24" x i8" for the intended use, is a massive piece of metal, integral braces as 39, are preferably supplied between. and connecting, the ledge 4| and upright 40.

The upper reach 400: of the upright is provided with a handle or cross-head 42, by which it may be raised and lowered, and in order that such operations may be effected easily and expeditiously, without imposing too much strain upon the operator and without undue danger of letting a plate be injured by dropping it, I have made provision for the support of the plate mechan ically for at least the greater part of its transit from one position to the other.

As a convenient construction for this purpose, I have illustrated a rod 44, having at its upper end a trough-shaped bracket 43, adapted to receive the cross-head 42 of the upright 40, while the shank 44a: of the rod is held slidingly for vertical adjustment in bearing brackets 45 and 46 extending horizontally from the compartment and from the container. The upper bracket 45 is shown as provided with a tit 41, adapted to index the rod in either of two indexing recesses 48 and 4! of the rod. This is shown clearly in Fig. 3, wherein the rod is at its low position,

with the plate-holder lowered to submerge the plates, as shown in Fig. 4; and; on the other hand, when the rod is at the high position shown in dash-dot lines in Fig. 4, the tit 41 will be engaged with the recess 48 of the rod. The rod is preferably of such a length that its lower end 50 At the upper end of the upright 40, suitable provision is made for a retainer device, to be engaged with upper portions of the plates, preferably at or near their upright side edges, in

order to permit a minimum of contact between the retainer and the plates.

Where two plates are to be submerged at once, the retainer may conveniently take the form shown in Fig. 6, in which a sleeve 5| is fitted to slide upon the upper reach 401: of the upright, and having a collar 52 by which it may be manipulated, the actual engagement with each of the plates being effected by a pair of complemental flanges, as 53 and 54, adapted to fit slidingly over the plate at each side of the upright, andthere embraced lightly.

In a modified form of retainer device not illustrated a collar (not shown) is anchored upon the upright and has a suitable pivot upon which are mounted swingingly a pair of retainer arms each of which has at its free end a finger or fingers adapted to be disposed in engagement only with an edge portion of the plate, at each side thereof.

Thearms are self-biased to this retentive position, and may be raised therefrom by suitable means, such as a cam or cams on a rotatable cam-carrier also mounted on the pivot, and having an operating handle.

As another modification of supporting means for the plate, I may provide loops of metal strip material, passing around the plate and over the cross-head in a manner which is not illustrated as it will be readily understood by those skilled in the art.

In further pursuance of the invention, I provide a pair of tongs, designated generally by the reference character T, and illustrated in Fig. '7,

having tong arms 63 anchored to a sleeve 65 and having fingers 64 at their free ends, to permit them to "grabf a plate when the tongs are to be used in the removal of a plate from the plateholder, an operation which does not require further elaboration. Similarly, when a plate is to be inserted in the plate-holder, it will be carried to the vicinity of the upright, while the latter occupies its high (Fig. 4) position, and the arms 63 of the tongs are preferably engaged with the plate edgesat a somewhat lower region, near their mid-points, both for ease in carriage, and so that they will clear the retainer arms when the latter are lowered to the position shown in Fig. 4 in dot-dash lines.

In Fig. 7, the tong elements 63 are shown in their position of rest, partly spread apart. and only requiring to be opened a slight further amount in order to be spaced far enough apart to extend over the edges of the plate as indicated in Fig. 4. This further opening is accomplished by pressing upon the handle 56 on plunger 51, which then enters between the knees 58 of the tongs and forces them apart until the tong elements can grasp the edges of a plate.

While I have shown the container H as of only sufiicient size to receive a single unit comprising one compartment I5 and plate receptacle IE, it will be understood that the container may be of suitable size to receive a plurality of such units, or to receive a developing unit as well as a sensitizing unit.

From the foregoing, the operation of the invention will be understood, but in order to air in such understanding, the following is given as a brief summary of the procedure In carrying into effect the method for the fabrication of plates for use in the printing art, after polishing both sides of a metal plate with a suitable abradant such as pumice, rinsing the plate to flush such abradant therefrom and whirling the plate to drain both sides thereof, both sides of said plate are provided with a sensitizing coating exclusively by submergence of the plate once in a bath of the sensitizing solution; then the plate may be whirled to distribute said coats evenly, to remove any excess of sensitizlng medium and to dry the latter; a primary negative of the image to be imposed upon said plate having been provided, as usual, a secondary negative is prepared therefrom either upon a sensitized film or upon a thin sensitized sheet of paper or suitable cellulosic material sufliciently transparent or translucent to permit photoprinting therethrough upon one side of said sensitized plate; then said print is superimposed upon one side of the sensitized plate, and said primary negative is superimposed upon the side of the sensitized plate which is to function as the printing surface thereof; both the sides of said assembly are then exposed to impose the image upon each side thereof; and both exposures are developed simultaneously to form a printing image upon one side and a bumper image upon the other side; and the method is completed by fixing said images simultaneously; and finishing both sides by known or suitable steps to secure the intended quality of each and to complete a protective coating upon the bumper side of the plate circumjacent to the bumper image.

Although I have particularly described one particular physical embodiment of my invention and explained the operation, construction and principle thereof, nevertheless, I desire to have it understood that the form selected is merely illustrative, but does not exhaust the possible physical embodiments of the idea of means underlying my invention.

What I claim as new and desire to secure by Letters Patent of the United States,- is:

1. In the fabrication of metal plates for use in the printing art; the method which comprises the steps of providing both sides of a metal plate with a light sensitive bichromated solution applied by dipping the metal plate into the solution to cover the front, back and edges of the plate to provide a light sensitive coating and a protective coating over the entire plate including the inactive surfaces of the plate to prevent access of etching solution to the portions of the plate so protected, thereby obviating completely the need for a special coating of other protective medium; preparing a negative with the image to be imposed upon said printing plate; preparing from said primary negative a positive; superimposing said primary negative upon one side of said sensitized plate; superimposing said positive upon the other sensitized side of said plate; exposing both sides of said assembly to impose the image upon each side of the plate; developing both exposures to produce a printing image upon one side of the plate and a bumper image upon the other side thereof; then etching both images to the desired extent to secure the desired printing qual- 2. The method according to claim 1, in which both sides of said assembly are exposed simul taneously.

3. The method according to claim 1, in which both sides of the assembly are exposed simultaneously for the same period.

4. The method of claim 1, in which said positive is prepared upon a suitable transparent vehicle such as a thin sheet of paper or like cellulosic material.

5. The method of providing a metal printing plate of the class described with a printable image upon one side and a protective coating upon the reverse side; said method comprising the steps of coating both sides of said plate with a coating of the same light sensitive bichromated solution applied by dipping the metal plate into the solution to cover the front, back and edges of the metal plate to provide a light sensitive coating and a protective coating over the entire plate including the inactive surfaces of the plate to prevent access of the etching solution to the portions of the plate so protected thereby obviating completely the need for a special coating of other protective medium; then exposing both sides of said plate to light, one through a photographic negative; then developing and fixing both sides of the plate by water whereby an image is produced on one side of the plate and a protective coating over the entire reverse side of the plate; then etching said image to the required depth for the quality of printing desired.

6. In the fabrication of metal plates for use in the printing art; the method which comprises the steps of polishing both sides of a metal plate with an abradant; rinsing the plate to flush said abradant therefrom; whirling the plate to drain both sides thereof; providing both sides of said plate with a sensitizing coating exclusively by submergence of the plate once in a bath of a light sensitive bichromated solution applied by dipping the plate into the solution to cover the front, back and edges of the plate to provide a light sensitive coating and a protective coating over the entire plate including the inactive sur faces of the plate to prevent access of etching solution to the portions of the plate so protected thereby obviating completely the need for a special coating of other protective medium; whirling the plate to distribute said coats evenly and to remove any excess of sensitizing medium and dry both sides; preparing a negative of the image to be imposed upon said plate; preparing from said negative a print upon a thin sensitized sheet of paper or suitable cellulosic material sufiiciently transparent to permit a photographic image to be produced therethrough upon one side of said sensitized plate; superimposing said print upon one side of the sensitized plate, and said negative upon the side of the sensitized plate which is to function as the printing surface thereof; exposing both sides of said assembly to impose the image-upon each side thereof; developing both exposures simultaneously to develop a printing image upon one side and a bumper image upon the other side; then etching said images to secure the required depth for the quality of printing desired and so have a printing image on one side of the plate, a bumper image on the other side of the plate and a protective coating over all of the plate other than that covered by the images.

ALBERT H. MAROOT. 

